The key is adjusting your 1/4" seam. I buy Log cabin laser cut strips from Jordan's of Oregon to make my Log Cabin quilts with. They are cut very true. I always have to adjust my 1/4" to make the logs come out even. Yes, it ends up a scant 1/4".
As several mentioned above, it may only be 1 tiny thread on the fabric over from where you think the true 1/4" seam is. Or it may be you need to move over 2 threads, if your sewing thread is a thick one. It's always the system of testing the 1/4" seam and measuring the finished product to find out how big the seam should be.
If you are making a 4 patch, or 9 patch where all the parts are even and you don't care if you come out with the block size mentioned in the pattern, then you can sew a true 1/4" seam. I always find that when I am dealing with many pieces and they are varying sizes, that I have to adjust that 1/4" seam to make the block come out the right size.
Last edited by Barb in Louisiana; 07-14-2015 at 06:38 AM.